Mineral cutter picks etc are used extensively not only for mineral winning, in particular coal mining, but also for the driving of underground roadways or tunnels, or for civil engineering purposes, such as road planing, as part of road re-surfacing operations, or trench cutting operations.
In practice, a series of blocks are attached e.g. by welding, around a drum, helical vane, or end face plate if a so-called shearer drum is involved, or attachment may be to an endless chain, each block having an aperture of profile matching that of a pick shank to be located in the aperture.
If coal mining is involved, the displacement of air to the area of the cut has long been recognised as advantageous in diluting methane released during mining. One proposal for achieving this development in the UK some decades ago, was to construct a shearer drum with a hollow annulus in which was located an array of water sprays to induce an air flow from the goaf or gob side to the face side of the drum.
One known water spray system is described in GB 2250455, where basically the pick is provided with a through hole in a rearwardly directed heel, and the head of a water spray nozzle, which is releasably retained within a bore of a block, projects above the block into the through hole, whereby the head of the nozzle, and its water discharge orifice are protected from damage and debris by the heel, so long as the pick remains intact and in situ.
It is not uncommon however for picks to be lost or broken for a variety of reasons. Sometimes, the retention system between pick shank and block fails. Sometimes, particularly during mineral winning operations, the picks inadvertently strike metal roof supports and are broken off. Such events lead to exposure, or potential exposure of the nozzle head, which eventually is wiped off upon continuation of mining operations.
One known staple latching system for a pick is described in U.S. Pat. No. 3,268,260. The staple was insertable, and removable in a horizontal plane, and the provision of a circumferential groove in the outer periphery of the shank introduces a zone of weakness.